/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package javax.servlet.jsp;

import java.io.IOException;

/**
 * <p>
 * The actions and template data in a JSP page is written using the JspWriter
 * object that is referenced by the implicit variable out which is initialized
 * automatically using methods in the PageContext object.
 * <p>
 * This abstract class emulates some of the functionality found in the
 * java.io.BufferedWriter and java.io.PrintWriter classes, however it differs in
 * that it throws java.io.IOException from the print methods while PrintWriter
 * does not.
 * <p>
 * <B>Buffering</B>
 * <p>
 * The initial JspWriter object is associated with the PrintWriter object of the
 * ServletResponse in a way that depends on whether the page is or is not
 * buffered. If the page is not buffered, output written to this JspWriter
 * object will be written through to the PrintWriter directly, which will be
 * created if necessary by invoking the getWriter() method on the response
 * object. But if the page is buffered, the PrintWriter object will not be
 * created until the buffer is flushed and operations like setContentType() are
 * legal. Since this flexibility simplifies programming substantially, buffering
 * is the default for JSP pages.
 * <p>
 * Buffering raises the issue of what to do when the buffer is exceeded. Two
 * approaches can be taken:
 * <ul>
 * <li>Exceeding the buffer is not a fatal error; when the buffer is exceeded,
 * just flush the output.
 * <li>Exceeding the buffer is a fatal error; when the buffer is exceeded, raise
 * an exception.
 * </ul>
 * <p>
 * Both approaches are valid, and thus both are supported in the JSP technology.
 * The behavior of a page is controlled by the autoFlush attribute, which
 * defaults to true. In general, JSP pages that need to be sure that correct and
 * complete data has been sent to their client may want to set autoFlush to
 * false, with a typical case being that where the client is an application
 * itself. On the other hand, JSP pages that send data that is meaningful even
 * when partially constructed may want to set autoFlush to true; such as when
 * the data is sent for immediate display through a browser. Each application
 * will need to consider their specific needs.
 * <p>
 * An alternative considered was to make the buffer size unbounded; but, this
 * had the disadvantage that runaway computations would consume an unbounded
 * amount of resources.
 * <p>
 * The "out" implicit variable of a JSP implementation class is of this type. If
 * the page directive selects autoflush="true" then all the I/O operations on
 * this class shall automatically flush the contents of the buffer if an
 * overflow condition would result if the current operation were performed
 * without a flush. If autoflush="false" then all the I/O operations on this
 * class shall throw an IOException if performing the current operation would
 * result in a buffer overflow condition.
 *
 * @see java.io.Writer
 * @see java.io.BufferedWriter
 * @see java.io.PrintWriter
 */
public abstract class JspWriter extends java.io.Writer {

	/**
	 * Constant indicating that the Writer is not buffering output.
	 */
	public static final int NO_BUFFER = 0;

	/**
	 * Constant indicating that the Writer is buffered and is using the
	 * implementation default buffer size.
	 */
	public static final int DEFAULT_BUFFER = -1;

	/**
	 * Constant indicating that the Writer is buffered and is unbounded; this is
	 * used in BodyContent.
	 */
	public static final int UNBOUNDED_BUFFER = -2;
	/**
	 * The size of the buffer used by the JspWriter.
	 */
	protected int bufferSize;
	/**
	 * Whether the JspWriter is autoflushing.
	 */
	protected boolean autoFlush;

	/**
	 * Protected constructor.
	 *
	 * @param bufferSize the size of the buffer to be used by the JspWriter
	 * @param autoFlush  whether the JspWriter should be autoflushing
	 */
	protected JspWriter(int bufferSize, boolean autoFlush) {
		this.bufferSize = bufferSize;
		this.autoFlush = autoFlush;
	}

	/**
	 * Write a line separator. The line separator string is defined by the
	 * system property <tt>line.separator</tt>, and is not necessarily a single
	 * newline ('\n') character.
	 *
	 * @throws IOException If an I/O error occurs
	 */
	public abstract void newLine() throws IOException;

	/**
	 * Print a boolean value. The string produced by <code>{@link
	 * java.lang.String#valueOf(boolean)}</code>
	 * is written to the JspWriter's buffer or, if no buffer is used, directly
	 * to the underlying writer.
	 *
	 * @param b The <code>boolean</code> to be printed
	 * @throws java.io.IOException If an error occurred while writing
	 */
	public abstract void print(boolean b) throws IOException;

	/**
	 * Print a character. The character is written to the JspWriter's buffer or,
	 * if no buffer is used, directly to the underlying writer.
	 *
	 * @param c The <code>char</code> to be printed
	 * @throws java.io.IOException If an error occurred while writing
	 */
	public abstract void print(char c) throws IOException;

	/**
	 * Print an integer. The string produced by <code>{@link
	 * java.lang.String#valueOf(int)}</code>
	 * is written to the JspWriter's buffer or, if no buffer is used, directly
	 * to the underlying writer.
	 *
	 * @param i The <code>int</code> to be printed
	 * @throws java.io.IOException If an error occurred while writing
	 * @see java.lang.Integer#toString(int)
	 */
	public abstract void print(int i) throws IOException;

	/**
	 * Print a long integer. The string produced by <code>{@link
	 * java.lang.String#valueOf(long)}</code>
	 * is written to the JspWriter's buffer or, if no buffer is used, directly
	 * to the underlying writer.
	 *
	 * @param l The <code>long</code> to be printed
	 * @throws java.io.IOException If an error occurred while writing
	 * @see java.lang.Long#toString(long)
	 */
	public abstract void print(long l) throws IOException;

	/**
	 * Print a floating-point number. The string produced by <code>{@link
	 * java.lang.String#valueOf(float)}</code>
	 * is written to the JspWriter's buffer or, if no buffer is used, directly
	 * to the underlying writer.
	 *
	 * @param f The <code>float</code> to be printed
	 * @throws java.io.IOException If an error occurred while writing
	 * @see java.lang.Float#toString(float)
	 */
	public abstract void print(float f) throws IOException;

	/**
	 * Print a double-precision floating-point number. The string produced by
	 * <code>{@link java.lang.String#valueOf(double)}</code> is written to the
	 * JspWriter's buffer or, if no buffer is used, directly to the underlying
	 * writer.
	 *
	 * @param d The <code>double</code> to be printed
	 * @throws java.io.IOException If an error occurred while writing
	 * @see java.lang.Double#toString(double)
	 */
	public abstract void print(double d) throws IOException;

	/**
	 * Print an array of characters. The characters are written to the
	 * JspWriter's buffer or, if no buffer is used, directly to the underlying
	 * writer.
	 *
	 * @param s The array of chars to be printed
	 * @throws NullPointerException If <code>s</code> is <code>null</code>
	 * @throws java.io.IOException  If an error occurred while writing
	 */
	public abstract void print(char s[]) throws IOException;

	/**
	 * Print a string. If the argument is <code>null</code> then the string
	 * <code>"null"</code> is printed. Otherwise, the string's characters are
	 * written to the JspWriter's buffer or, if no buffer is used, directly to
	 * the underlying writer.
	 *
	 * @param s The <code>String</code> to be printed
	 * @throws java.io.IOException If an error occurred while writing
	 */
	public abstract void print(String s) throws IOException;

	/**
	 * Print an object. The string produced by the <code>{@link
	 * java.lang.String#valueOf(Object)}</code>
	 * method is written to the JspWriter's buffer or, if no buffer is used,
	 * directly to the underlying writer.
	 *
	 * @param obj The <code>Object</code> to be printed
	 * @throws java.io.IOException If an error occurred while writing
	 * @see java.lang.Object#toString()
	 */
	public abstract void print(Object obj) throws IOException;

	/**
	 * Terminate the current line by writing the line separator string. The line
	 * separator string is defined by the system property
	 * <code>line.separator</code>, and is not necessarily a single newline
	 * character (<code>'\n'</code>).
	 *
	 * @throws java.io.IOException If an error occurred while writing
	 */
	public abstract void println() throws IOException;

	/**
	 * Print a boolean value and then terminate the line. This method behaves as
	 * though it invokes <code>{@link #print(boolean)}</code> and then
	 * <code>{@link #println()}</code>.
	 *
	 * @param x the boolean to write
	 * @throws java.io.IOException If an error occurred while writing
	 */
	public abstract void println(boolean x) throws IOException;

	/**
	 * Print a character and then terminate the line. This method behaves as
	 * though it invokes <code>{@link #print(char)}</code> and then <code>{@link
	 * #println()}</code>
	 * .
	 *
	 * @param x the char to write
	 * @throws java.io.IOException If an error occurred while writing
	 */
	public abstract void println(char x) throws IOException;

	/**
	 * Print an integer and then terminate the line. This method behaves as
	 * though it invokes <code>{@link #print(int)}</code> and then <code>{@link
	 * #println()}</code>
	 * .
	 *
	 * @param x the int to write
	 * @throws java.io.IOException If an error occurred while writing
	 */
	public abstract void println(int x) throws IOException;

	/**
	 * Print a long integer and then terminate the line. This method behaves as
	 * though it invokes <code>{@link #print(long)}</code> and then
	 * <code>{@link #println()}</code>.
	 *
	 * @param x the long to write
	 * @throws java.io.IOException If an error occurred while writing
	 */
	public abstract void println(long x) throws IOException;

	/**
	 * Print a floating-point number and then terminate the line. This method
	 * behaves as though it invokes <code>{@link #print(float)}</code> and then
	 * <code>{@link #println()}</code>.
	 *
	 * @param x the float to write
	 * @throws java.io.IOException If an error occurred while writing
	 */
	public abstract void println(float x) throws IOException;

	/**
	 * Print a double-precision floating-point number and then terminate the
	 * line. This method behaves as though it invokes <code>{@link
	 * #print(double)}</code> and
	 * then <code>{@link #println()}</code>.
	 *
	 * @param x the double to write
	 * @throws java.io.IOException If an error occurred while writing
	 */
	public abstract void println(double x) throws IOException;

	/**
	 * Print an array of characters and then terminate the line. This method
	 * behaves as though it invokes <code>print(char[])</code> and then
	 * <code>println()</code>.
	 *
	 * @param x the char[] to write
	 * @throws java.io.IOException If an error occurred while writing
	 */
	public abstract void println(char x[]) throws IOException;

	/**
	 * Print a String and then terminate the line. This method behaves as though
	 * it invokes <code>{@link #print(String)}</code> and then
	 * <code>{@link #println()}</code>.
	 *
	 * @param x the String to write
	 * @throws java.io.IOException If an error occurred while writing
	 */
	public abstract void println(String x) throws IOException;

	/**
	 * Print an Object and then terminate the line. This method behaves as
	 * though it invokes <code>{@link #print(Object)}</code> and then
	 * <code>{@link #println()}</code>.
	 *
	 * @param x the Object to write
	 * @throws java.io.IOException If an error occurred while writing
	 */
	public abstract void println(Object x) throws IOException;

	/**
	 * Clear the contents of the buffer. If the buffer has been already been
	 * flushed then the clear operation shall throw an IOException to signal the
	 * fact that some data has already been irrevocably written to the client
	 * response stream.
	 *
	 * @throws IOException If an I/O error occurs
	 */
	public abstract void clear() throws IOException;

	/**
	 * Clears the current contents of the buffer. Unlike clear(), this method
	 * will not throw an IOException if the buffer has already been flushed. It
	 * merely clears the current content of the buffer and returns.
	 *
	 * @throws IOException If an I/O error occurs
	 */
	public abstract void clearBuffer() throws IOException;

	/**
	 * Flush the stream. If the stream has saved any characters from the various
	 * write() methods in a buffer, write them immediately to their intended
	 * destination. Then, if that destination is another character or byte
	 * stream, flush it. Thus one flush() invocation will flush all the buffers
	 * in a chain of Writers and OutputStreams.
	 * <p>
	 * The method may be invoked indirectly if the buffer size is exceeded.
	 * <p>
	 * Once a stream has been closed, further write() or flush() invocations
	 * will cause an IOException to be thrown.
	 *
	 * @throws IOException If an I/O error occurs
	 */
	@Override
	public abstract void flush() throws IOException;

	/**
	 * Close the stream, flushing it first.
	 * <p>
	 * This method needs not be invoked explicitly for the initial JspWriter as
	 * the code generated by the JSP container will automatically include a call
	 * to close().
	 * <p>
	 * Closing a previously-closed stream, unlike flush(), has no effect.
	 *
	 * @throws IOException If an I/O error occurs
	 */
	@Override
	public abstract void close() throws IOException;

	/**
	 * This method returns the size of the buffer used by the JspWriter.
	 *
	 * @return the size of the buffer in bytes, or 0 is unbuffered.
	 */
	public int getBufferSize() {
		return bufferSize;
	}

    /*
     * fields
     */

	/**
	 * This method returns the number of unused bytes in the buffer.
	 *
	 * @return the number of bytes unused in the buffer
	 */
	public abstract int getRemaining();

	/**
	 * This method indicates whether the JspWriter is autoFlushing.
	 *
	 * @return if this JspWriter is auto flushing or throwing IOExceptions on
	 * buffer overflow conditions
	 */
	public boolean isAutoFlush() {
		return autoFlush;
	}
}
